Add -i/--input option to locale(1)

The default UI language returned by GetUserDefaultUILanguage does not
necessarily reflect what the user really wants.  E. g., the system could
be en_US, but the desired language is en_CA, without having a CA langpack
installed.

Changing the settings under "Languages" and changing the keyboard layout
is only affecting the so-called  "Input language", while what's returned
by GetUserDefaultUILanguage is the "Display language".  Changing the
latter requires installing MUI langpacks.

Thus, we introduce a way to fetch the "Input language" using the -i or
--input option.

Also clean up documentation of locale(1).

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/doc/utils.xml

@@ -787,7 +787,7 @@ ldd [OPTION]... FILE...
       <screen>
 locale [-amvhV]
 locale [-ck] NAME
-locale [-usfnU]
+locale [-iusfnU]
       </screen>
     </refsynopsisdiv>
 
@@ -807,6 +807,7 @@ Modify output format:
 
 Default locale information:
 
+  -i, --input          Print current input locale
   -u, --user           Print locale of user's default UI language
   -s, --system         Print locale of system default UI language
   -f, --format         Print locale of user's regional format settings
@@ -826,20 +827,34 @@ Other options:
     <para><command>locale</command> without parameters prints information about
       the current locale environment settings.</para>
 
-    <para>The <literal>-u</literal>, <literal>-s</literal>,
-      <literal>-f</literal>, and <literal>-n</literal> options can be used to
-      request the various Windows locale settings. The purpose is to use this
-      command in scripts to set the POSIX locale variables.</para>
+    <para>The <literal>-i</literal>, <literal>-u</literal>,
+      <literal>-s</literal>, <literal>-f</literal>, and <literal>-n</literal>
+      options can be used to request the various Windows locale settings. The
+      purpose is to use this command in scripts to set the POSIX locale
+      variables.</para>
+
+    <para>The <literal>-i</literal> option prints the current input language.
+      This is called the "Input language" and basically equivalent to the
+      current keyboard layout setting.</para>
 
     <para>The <literal>-u</literal> option prints the current user's Windows UI
       locale to stdout. In Windows this setting is called the
-      "Display Language". The <literal>-s</literal> option prints the systems
-      default instead. The <literal>-f</literal> option prints the user's
-      setting for time, date, number and currency. That's equivalent to the
-      setting in the "Formats" or "Regional Options" tab in the "Region and
-      Language" or "Regional and Language Options" dialog. With the
-      <literal>-U</literal> option <command>locale</command> appends a
-      ".UTF-8".</para>
+      "Display Language".</para>
+
+    <para>The <literal>-s</literal> option prints the systems default instead.
+    </para>
+
+    <para>The <literal>-f</literal> option prints the user's setting for time,
+      date, number and currency. That's equivalent to the setting in the
+      "Formats" or "Regional Options" tab in the "Region and Language" or
+      "Regional and Language Options" dialog.</para>
+
+    <para>The <literal>-n</literal> option prints the system's default
+      language used for applications which don't support Unicode.</para>
+
+    <para>With the <literal>-U</literal> option <command>locale</command>
+      appends the string ".UTF-8" to enforce using UTF-8.  Using UTF-8
+      as codeset is recommended.</para>
 
     <para>Usage example:</para>
 

winsup/utils/locale.cc

@@ -48,7 +48,7 @@ usage ()
   printf (
 "Usage: %1$s [-amvhV]\n"
 "   or: %1$s [-ck] NAME\n"
-"   or: %1$s [-usfnU]\n"
+"   or: %1$s [-iusfnU]\n"
 "\n"
 "Get locale-specific information.\n"
 "\n"
@@ -65,6 +65,7 @@ usage ()
 "\n"
 "Default locale information:\n"
 "\n"
+"  -i, --input          Print current input locale\n"
 "  -u, --user           Print locale of user's default UI language\n"
 "  -s, --system         Print locale of system default UI language\n"
 "  -f, --format         Print locale of user's regional format settings\n"
@@ -93,6 +94,7 @@ struct option longopts[] = {
   {"category-name", no_argument, NULL, 'c'},
   {"format", no_argument, NULL, 'f'},
   {"help", no_argument, NULL, 'h'},
+  {"input", no_argument, NULL, 'i'},
   {"keyword-name", no_argument, NULL, 'k'},
   {"charmaps", no_argument, NULL, 'm'},
   {"no-unicode", no_argument, NULL, 'n'},
@@ -103,7 +105,7 @@ struct option longopts[] = {
   {"version", no_argument, NULL, 'V'},
   {0, no_argument, NULL, 0}
 };
-const char *opts = "acfhkmnsuUvV";
+const char *opts = "acfhikmnsuUvV";
 
 int
 getlocale (LCID lcid, char *name)
@@ -786,6 +788,9 @@ main (int argc, char **argv)
       case 'm':
 	maps = 1;
 	break;
+      case 'i':
+	lcid = (UINT_PTR) GetKeyboardLayout (0) & 0xffff;
+	break;
       case 's':
 	lcid = GetSystemDefaultUILanguage ();
 	break;